Setting Up cable modem to ISP.

[mr2000]

Hi all.

Im trying to setup my E0/0 on a 2611 to interface to my ISP (RJ45 handoff), but dont know how to get the ip address of the cable modem. i can use winipcfg to get my address, but not the cable modem. Also, how do i configure this address as the ip is on a lease????

Once i get this address Im planning to use e0/1 as my lan interface and set up routing between the two. Is this the best way to do this, as I have seen other posts where people have back to back 2501's etc. I have access to a range of routers inc 1600's, 2500's and 2600's.

All help gratefully recieved.

 

[UNIX72]

Check out thread 557-36765 shows you how to config the router to a cable modem, works well with me!

 

[wybnormal]

Normally speaking, cable "modems" are really a bridge without an IP address. The easiest way to find out the nexthop is to use the PC that the cable company knows about and just run a traceroute to a host. Depending on if you a third party traceroute or MS, you will get the next hop in either the 1st or 2nd line.

The 2611 works nicely as you want it, I happen to use a 2514 the same way. No need for back to back or other trickery with the dual ethernet port. Just remember to setup NAT on the router for the outside port which would be E0/0 That way you can share the one IP the cable company gave you. The only issue you might have is if the cable company does DHCP for your address.

Mike S
"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[mr2000]

Thanks for the speedy responses.

Update:::::

I disabled my cable modem acting as DHCP, and run a traceroute from my pc to a known host. I get a 10.x.x.x as my first hop (bridge in modem????) and then the gsr router at my isp. Neither of these addresses is the same as the winipcfg address normally obtained on my pc.
So i can ping from the router and get external access now, but none of the clients from e0/1 can access the outside world. i can ping the e0/1 interface, and thats it. Ive set up nat outside on e0/0 and inside on e0/1. when i do an ip route statement the given ip address for e0/1 is one less than the configured interface address.
Also, when browsing, I ge the message "opening site

http://www.xxx.com,

but then the dreaded 404. Does this mean the outgoing packet gets to the site, but there is a problem with the incoming which stops me browsing/poinging/tracerouteing. Sorry for the length of the reply, but I feel its all relevant.

Thanks.

 

[chdavisjr]

I don't have an answer for mr2000, but I have a question for UNIX72 ... how do I get to thread 557-36765? I have a feeling it has the answers that I need, but I see nothing here that lets me go directly to another thread.
Sincerely,
Chalmers Davis

 

[migueljr3]

http://www.cisco.com/warp/public/109/router_behind_cm_19268.shtml

This worked for me, very simple I have a 2514 running this config.

Migo CCNA,MCP,Net+,A+